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API Nitrate Test Kit for Freshwater and Saltwater Aquariums

API  |  SKU: 740737S


Measures nitrate levels in both fresh & saltwater aquariums. Tests nitrate levels from 0 to 160 ppm. 90 tests per kit. 


Effective for both fresh & saltwater aquariums. High levels of nitrate are a food source for unwanted algae & indicate poor water quality & health problems for fish. Tests nitrate levels from 0 to 160 ppm.

Freshwater/Saltwater Nitrate Test Instructions:

Why Test For Nitrate?
Nitrate (NO3-) is produced in the aquarium by the biological filter. Beneficial bacteria in the biological filter convert toxic ammonia and nitrite into nitrate. A high nitrate level indicates a build-up of fish waste and organic compounds, resulting in poor water quality and contributing to the likelihood of fish disease. Excessive nitrate also provides a nitrogen source that can stimulate algal blooms. In the opinion of many aquarists, maintaining a low nitrate level improves the health of fish and invertebrates.

Testing Tips:
This test kit reads total nitrate (NO3-) level in parts per million (ppm) which are equivalent to milligrams per liter (mg/L) from 0 ppm to 160 ppm, in either fresh or saltwater aquariums. This kit includes two Nitrate Test Color Charts — one for freshwater aquariums, and one for saltwater aquariums — so be sure to use the correct chart for your type of aquarium when interpreting test results. The Freshwater Nitrate Test Color Chart is the appropriate chart to use for testing freshwater aquariums to which salt has been added. This test kit measures nitrate as nitrate ion or “total nitrate.” Other nitrate test kits that measure “nitrate-nitrogen” (NO3-N) will give readings 4.4 times LESS than this test kit.



  • Are high nitrate levels harmful to fish?

High nitrate is harmful to fish, but is significantly less toxic than ammonia or nitrite. Effects of high nitrate levels are more gradual if parameters go untreated – fish will eventually lose their appetite and grow sluggish and inactive over time. High nitrate also contributes to rapid algae blooms in aquariums.


  • How often should I use API NITRATE TEST KIT?

Use API NITRATE TEST KIT weekly or bi-weekly to ensure your nitrate levels are safe for fish, or whenever you suspect you may have high nitrate levels in your tank.


Directions for Testing Nitrate:

  • Read thoroughly before testing. Do not allow Test Solutions to get into the aquarium.
  • To remove the childproof safety cap: With one hand, push red tab left with your thumb while unscrewing the cap with your free hand.
  • Fill a clean test tube with 5 ml of water to be tested (to the line on the tube).
  • Add 10 drops from Nitrate Test Solution Bottle # 1, holding the dropper bottle upside down in a completely vertical position to assure uniformity of drops added to the water sample.
  • Cap the test tube and invert the tube several times to mix the solution. Do not hold your finger over the open end of the tube, as this may affect test results.
  • Vigorously shake the Nitrate Test Solution Bottle # 2 for at least 30 seconds. This step is extremely important to insure the accuracy of test results.
  • Now add 10 drops from Nitrate Test Solution Bottle #2, holding the dropper bottle upside down in a completely vertical position to assure uniformity of drops to the water sample.
  • Cap the test tube and shake vigorously for one minute. This step is extremely important to insure the accuracy of test results.
  • Wait five minutes for the color to develop.
  • Read the test results by matching the color of the solution against those on the Nitrate Test Color Chart. The tube should be viewed against the white area beside the color chart. Color comparisons are best made in a well-lit area. The closest match indicates the ppm (mg/L) of nitrate in the water sample. Rinse the test tube with clean water after each use. 


What The Test Results Mean:
In new freshwater and saltwater aquariums, the nitrate level will gradually climb as the biological filter becomes established. A nitrate level of 40 ppm (mg/L) or less is recommended for freshwater aquariums. Many marine aquarists prefer to keep nitrate levels as low as possible, especially when keeping invertebrates.

Monitoring Nitrate Levels:
Regular testing for nitrate is an essential part of routine aquarium maintenance. Aquarium water should be tested for nitrate once a week to make sure the nitrate does not reach an undesirable level.

Reducing Nitrate:

In Saltwater
Partial water changes are the easiest way to lower the nitrate in a saltwater aquarium. Keep in mind, however, that the biological filter constantly produces nitrate.

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